Investigating the interaction between asphalt binder and fresh and simulated RAP aggregate

• A method to evaluate binder-aggregate interaction was developed.
• Interaction between binder and aggregate initially increases stiffness of the binder with time and then decreases.
• Higher curing temperature and/or longer curing times produce greater interaction and shear strength of RAP interfaces.

Although the role of individual ingredients of hot mix asphalt (HMA) such as asphalt binder and aggregates on its performance is readily recognized, there is only limited understanding about the interactions between these components and the properties of binder-aggregate interface. In order to study the interactions between asphalt binder and mineral aggregates, an interfacial test method was developed and its effectiveness was evaluated. Interfacial interactions were evaluated by testing thin films of an asphalt binder interfaced with the surface of aggregates under two different modes of loading in shear: sinusoidal oscillation and monotonically increasing. An Interaction Parameter (IP) was proposed to quantify the binder-aggregate interfacial effects. The results show that the methodology used in this study can quantify the effects of interaction between the asphalt binder and mineral aggregates. Furthermore, this research also investigated the interaction of an asphalt binder with the surface of simulated reclaimed asphalt pavement (RAP) aggregates. The results from this research not only provide an insight to the effects of binder-aggregate interaction, but can also help practitioners to better understand the effect of mixing conditions on the properties of mixtures produced using different materials.

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